This invention relates generally to a concrete finishing machine.
As is well known to those skilled in the concrete finishing art, wet concrete, which has been poured into a form such as that used in the construction of floors and the like, is troweled during the hardening period in order to produce a smooth, bubble free surface. During the troweling process, water contained in the wet concrete rises to the surface of the concrete and evaporates therefrom leaving a smooth surface. In addition, such troweling compacts the concrete and increases its strength.
Within approximately the last three decades, mechanized devices for troweling large expanses of concrete have been developed and put into commercial use. Through the use of such machines concrete may be finished at a much more rapid pace and with an increase in the quality and surface smoothness of the finished concrete.
Exemplary of early troweling machines is that disclosed in U.S. Pat. No. 2,594,331 (1952) to McCrery. As is generally disclosed in the McCrery patent, such machines typically comprise a housing, a motor of some type enclosed within the housing, a rotatable shaft connected to the motor and extending vertically downwardly from the housing and a plurality of spider arms extending from the rotatable shaft. Each spider arm carries a troweling blade, which is approximately rectangular having an outer, or distal, end. A guard ring encircles the device outwardly adjacent the outer ends of the blades to prevent any accidental contact with the blades during operation. The guard ring is supported in this position, slightly above the surface of the concrete being troweled, by one or more guard ring stabilizer arms, which are, themselves attached to the housing. A handle extends upwardly and radially from the housing and is equipped with manually operable devices for controlling the machine function.
In operation the motor is actuated and causes the rotatable shaft, and therefore the troweling blades, to rotate. The handle is used by the operator to manipulate the machine in the direction of the wet concrete he wishes to smooth. During the initial stages of the troweling operation while the concrete is still wet, the troweling blades are oriented parallel to the concrete surface in order that the weight of the machine is distributed evenly over their large surface area. As the concrete hardens, however the blades are tilted by the operator such that an increasing portion of the machine weight is borne by the trailing edge of each blade. By so doing the effective pressure (in pounds per square inch) is gradually increased as the hardening of the concrete progresses.
The basic design described hereinabove is still used in modern conventional machines. In addition, it is also known to provide a stabilizer ring which is attached to either the spider arms or to the troweling blades themselves adjacent their outer, or distal, ends. The use of such a stabilizer ring reduces the "wobble" between the blades and increases the efficiency of operation of the machine.
In addition to the patent to McCrery, several patents have issued to inventors for improvements in the blade attaching mechanisms which allow quicker or more efficient removal and replacement of such blades. Exemplary of such patents are U.S. Pat. Nos. 2,667,824 to McCrery, 3,296,946 to Cagno and 3,402,647 to Colizza et al.
Each of the three aforementioned patents attempts to solve the problem of facilitating blade replacement. Nevertheless, there remain greater problems associated with the use of automatic troweling machines. Specifically, these problems arise because certain concrete troweling jobs are more efficiently done with a certain size of troweling machine. For example, a large expanse of concrete such as that found in a large parking garage or warehouse is obviously amenable to being troweled with a troweling machine which has a large troweling diameter, i.e., a large distance between the distal ends of opposite blades. On the other hand, small portions of concrete such as contained in sidewalks, garages, and basemenet floors require a smaller diameter machine in order to enable the operator to avoid obstructions and to fit in tight corners. Finally, small shower or bath rooms and the like are most readily troweled by a machine of still smaller diameter. This need, i.e., for variety of troweling diameters has been met merely by the manufacture of several machines with various troweling diameters.
For this reason, a rental supplier of such machines, or a contractor who owns such machines, must stock a number of each of the various size machines which may be preferred for the various jobs.
In other words since each individual machines is constructed in a fashion similar to that shown in the McCrery reference, i.e. with a fixed diameter guard ring, in order to have "46-inch", a "36-inch" and a "30-inch" troweling capability, one must now own three machines having different diameters of the guard ring and different lengths of the troweling blades.
In addition, due to the lack of standarization in the means used to attach the troweling blades to the spider arms manufactured by the various machine makers, a machine user is restricted in his purchase or replacement troweling blades to the blade type manufactured by the maker of the particular machine involved.
Such blade types include the "bar type" in which the planar blade is bonded to a narrow bar-like backbone which extends for a substantial portion of the length of the blade and which includes means for securing it to the spider arm. Even within the general "bar type" category, individual manufacturers' blades may vary in the width, length or height of the bar as well as in the type and placement of the means for securing the bar to the spider arm. A second general type of blade is the "channel type." This type is characterized by the inclusion of two walls, perpendicular to the blade and parallel to each other, on the top of the blade, which extend for a substantial portion of the length of the blade. These two parallel walls and that portion of the blade top therebetween form a channel. Once again suitable means for securing the channel means to the spider arm are used.
It is accordinally, an object of the present invention to provide a troweling machine which will allow the substitution of various lengths of troweling blades on a single machine.
It is a further object to provide a troweling machine with a variable troweling diameter.
It is a still further object to provide guard rings which are adjustable in diameter and so arranged as to permit ready replacement of different blades and adjustment of troweling diameters.
It is a still further object of this invention to provide a troweling machine which is capable of accepting any of the various troweling blades made by the various blade manufacturers.